i78 THE STRUCTURE OF ECONOMIC PLANTS 



occupies the central portion of the flower; and, although carpels 

 are commonly supplied with three bundles (a central bundle and 

 two marginal ones), in this instance the marginal bundles have 

 been suppressed, and each carpel is supplied by a single vascular 

 strand. The carpellary bundles are derived from the cortical 



bundles of the receptacle, 

 and are so differentiated 

 that two of them constitute 

 direct branches of two of 

 the cortical bundles which 

 lie opposite them while a 

 third carpellary bundle is 

 the product of a fusion of 

 two vascular strands de- 

 rived from adjacent cor- 

 tical bundles. In some 

 instances, these two bundles 

 remain distinct so that the 

 upper part of the pistil may 

 contain four bundles in- 

 stead of three. After the 

 divergence of the vascular 

 strands to the sepals and 



Fig. 1^8. Diagrammatic series of sections through i r u • i 



flower to illustrate origin and course of vascular Catpels from the COttlCal 



supply; A, section through base of receptacle bundles, the distal SeCtionS 

 showing five peripheral bundles and sixth one (. . ^^^ stamenS, 



in close proximity to base of ovary cavity ; B, sec- r 



tion taken at slightly higher level, bundle Qo each being supplied by a 



forms vascular supply of single ovule (W); C, sec- g-^jg bundle. (FlZ. 1^8, 

 tion at level where sepals are differentiating and & ■ \ b J ' 



peripheral bundles are branching. Four strands D.) 



designated (<r form vascular supply of three MiCROSPOROGENESIS. — 

 carpels; D, section through upper part of flower ■ r ai 



showing distinct sepals dO- The filaments of MlCrOSporOgeneSlS follOWS 



stamens are still part of glandular disk region Qgl dt). ^J^g general Sequence that 

 Each stamen is supplied with a single trace (st 0- • ^ „ ^„„;^ 



(After Artschwager.V- ^^r R...) OCCUtS in many anglO- 



sperms, although Matthy- 

 sen (ii) has noted some differences in the early prophases; and 

 the sporogenous tissue of the young anther develops rapidly to the 

 mother cell stage. Each pollen grain contains nine chromosomes, 

 which is the haploid number reported for the genus and for many 

 other members of the Chenopodiaceae. Matthysen reports find- 

 ing eight chromosomes for the cultivated garden beet; but this 



